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Bootloader: Optimize some unnecessary branches on carry add/sub

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Bananymous
2024-01-03 17:05:33 +02:00
parent 2a68df81e2
commit 7356a83a44
2 changed files with 4 additions and 9 deletions
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10
bootloader/bios/disk.S
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@@ -389,10 +389,8 @@ find_root_partition:
# increment 8 byte entry array lba
incl 0(%esp)
jnc .find_root_partition_no_overflow
incl 4(%esp)
adcl $0, 4(%esp)
.find_root_partition_no_overflow:
# loop to read next section if entries remaining
cmpl $0, 12(%esp)
jnz .find_root_partition_read_entry_section
@@ -416,12 +414,10 @@ find_root_partition:
# ebx:eax -= first lba - 1
subl (root_partition_entry + 36), %ebx
movl (root_partition_entry + 32), %ecx;
movl (root_partition_entry + 32), %ecx
decl %ecx
subl %ecx, %eax
jnc .find_root_partition_count_sub_no_carry
decl %ebx
.find_root_partition_count_sub_no_carry:
sbbl $0, %ebx
# ecx: min(partition count, 0xFFFFFFFF)
movl $0xFFFFFFFF, %edx